Need to install a shim kit, replace a
leaking flange seal, or just swap in a different size flange? These pics
will hopefully help out!

First, a pic of the tools I'll be using to
change the flange. Circlip pliers, screw driver,
home made flange tool, 17mm wrench, 8mm wrench, and some bubblegum scented
gloves.

Here is a better pic of the homemade tool.
As you will see in other pics, a welder I am not! It is good enough for my
needs however blobby it may be.

It is a M10 x 1.50 piece of threaded rod, a
couple M8 x 1.25 bolts, a couple M10 nuts, and a tube with a couple of bars
welded on. The tube is a piston wrist-pin from a 1.8 8V. I spaced the bars
out so they can sit on the head of the M8 bolts when assembled on the
flange.

The old tool doubles as a flange puller, but you can accomplish this by threading in 2 of the M8x1.25 bolts through the flange until they hit the trans case, then tighten them evenly to walk the flange off.

Here is a pic of a homemade flange compression tool I am now making, I have a jig built to fold the steel and make the tool.... actually, that is an older pic, I'm now making them out of 8mm (5/16") thick steel so they are stronger. If you are interested in buying one, I sell them for $30 shipped, just Email Me to purchase one.

The first thing you will need to do is to
remove the center cap seal in the middle of the flange. There are 2 kinds of
seals, one with a rubber center, and one that is all steel. On the rubber
version seals, you can stab a screwdriver through it and pry the seal out,
but on the steel seals, you might find it easier to lever the seal out from
the edge.

The front of the seals look the same, but
poke the center and you'll know if it is rubber or not.

Here is the backside of the above seals,
the one on the left is all steel, the one on the right is rubber in the
center. You can see where the steel seal has been hit before, and wasn't
punctured.

While on the topic of various parts you
might find, here is a pic of the 2 types of concave washers that VW used
under the circlip that holds the flange. I am not aware of what exactly the
difference is, or why the design changed just yet, if you know, let me
know:)

OK, lets dig that center seal out, and for
the pics, I used the steel version, and how to pry it out from the side. Be
careful not to dig into the flange as you lever it out. Pressing the tip of
the screwdriver into the soft rubber and levering will usually pop the seals
out.

OK, the seal is out, the circlip is
exposed, and it is time to remove it. At this point, you can just knock the
circlip out of the groove with a screwdriver, yank it out, and the flange
should just pop up off the shaft.

For the pics, I will show the tool being
used to compress the spring behind the flange to make the circlip easier to
remove.

Thread the M8 bolts into the flange and
thread the M10 rod into the center of the stub axle in the middle of the
flange. Bottom the M10 bolt and snug it up. Place the bars of the tool over
the tops of the M8 bolts, and now tighten the top 17mm nut to force the
tube/bolts/flange down, and release the spring tension on the circlip.

Reach in with your handy-dandy circlip
pliers, a good set of these are priceless when fighting a circlip in a
confined area such as with the flange. These are Snap-On SRP5A pliers, and
they work pretty well.

Once the circlip is removed, release the
tension by backing the flange tool off

The flange most likely will pop off under
the spring pressure and remove itself from the stub axle, but if it doesn't
you can either thread in a couple M8 bolts into something solid behind the
flange, and drive the flange off by evenly walking the bolts in....or you
can reverse the use of the home made flange tool, and place the bars under
the M8 bolts, and unscrew the bottom 17mm nut, and it will lift the flange
off the axle stubs.

Once the flange is off, you'll be able to
see the diff carrier taper bearing, and the stub axle, and then the bronze
conical thrust ring. It very well may be in more than one piece. Normally,
they are not a complete ring, and they do have a gap which looks like the
ring has broken, but it is supposed to be there. If the ring is broken, it
will be in more than one piece.

If it is broken in, say, 2 or 3 clean
pieces, then it can be re-used, because once assembled, the pieces cannot go
anywhere, and they'll still do their job.

They were added in there, along with the
springs, to stop the stub axles from making a noise because of slop in the
parts. The rings and springs add a bit of tension to the stub axles, and
make them quiet. This tension is what is increased by the 40% and 80% shim
kits.

Here is a better pic of the split in the
ring that looks like a crack. To get the ring out, use a small pick or
screwdriver to spin the ring around, and this will break the surface tension
of the oil, and allow it to be slid off of the shaft.

Here you can see the flange, the spring
that fits onto the bottom of the flange, then the spring cap.

The install is pretty much the reverse of
the removal, to remove the flange seal, simply lever it out once the flange
is removed. Be sure to coat the new seal in trans fluid to allow the seal to
be installed smoothly. Also pack the inside of the seal lips with grease.

Use a tube the right size to allow you to
press the seal in fully...

There is a spring behind the dust lip of
the seal, don't allow that lip to roll up or the spring could pop out, and
result in a leak.

When installing the circlip, VW suggest the
use of special tool 30-23 to help seat the circlip in the groove if needed.
The special tool is just a tube with an ID of 26mm to fit over the stub
axle, but still catch the circlip. Use it to knock the circlip in and seat
it fully.

Instead of the special tool, you can simply
walk around the circlip with a flatblade screwdriver, shoving it into the
groove and seating it fully by tapping the screw driver with a hammer as you
seat it. Start in the middle, and work your way to the each end of the clip
until it is fully seated.

Pop in a new cap seal in the center of the
flange, and the job is done.

Here is a pic of how to use big clamps as
the compression tool, thanks to 'nobber'
for the use of the pic!

A pic showing the 100mm next to a 90mm
flange on the trans, the 90mm is on the bottom trans.

Where to measure across to get the 90mm or
100mm measurement.

You can also measure the inner CV joint itself, and determine
the size.

Take a piece of string and wrap it around
the inner CV joint, right where it fits into the flange.... mark the string
where it meets itself, so you know how far it is around the CV joint.
Measure the string.

A bit over 11" (11.13) and it is a 90mm
CV/flange.
Just under 12.5" (12.36) and it is a 100mm CV/flange.

Flange Seal Info

There are 2 types of seal, the new types
are 50x65x10 in size, while the older seals are 36x58x15 in size. The new
seal is 7.5mm wide, and the old seal is 11mm wide, they're sometimes called
'fat' seals. The fat seals can be found on trans before 1983 and you can
quick check to see if the trans has the old seals or the new seals... look
for the green sleeve.

The green sleeve on just the passenger side
means it has all new style parts (flanges, seals, springs, thrust cones,
diff carrier), and this will be a 1983+ trans. The factory also released
some I think that used 2 green sleeves, one on each side, and it was during
the transition period I think between the 2 case designs for the new seals.
These trans will have all new parts, but the case will be older.

A trans without any green sleeve is going
to be an older unit, and it will use the old fat seals.

The seals being used will tell you about
the flanges... there are old and new style 90mm flanges, and then there are
100mm flanges. The 100mm and the new style 90mm flanges use the new style
seals, the 50x65x10 seals. The old style 90mm flanges use the old fat seals.

Converting a 100mm trans to 90mm

You can't put the old style 90mm flanges or
seals into a new case, the hole machined into the aluminum is too large. You
have to use new 90mm flanges in the new seals to make the trans 90mm. The
new 90mm flanges will fit right into the existing seals and sleeve and will
be able to use the springs and cones behind the flanges.

Converting a 90mm trans to 100mm

If the trans has a green sleeve in it, then
it is new style, just find some 100mm flanges, and pop them in. If it has 2
green sleeves, it should be a direct fit, but if you find for some reason
that there are no springs or cones behind the old flanges, then you can
still use the new 100mm flanges, just without the springs and cones... the
diff carrier inside would determine if the cones and springs can be used
(basically, if you have a place for the cones in the carrier), but either
way, the new 100mm flanges can be used if the trans has 1 or 2 green
sleeves.

If the 90mm trans has no green sleeves at
all, then it has old style 90mm flanges, and it is using the old style fat
seals, and has no springs or cones behind it, and likely the diff carrier
can't use them anyway. To make them 100mm, you need 2 green sleeves, 2 new
flange seal kits, and obviously a pair of 100mm flanges. The green sleeves
will convert the small holes into larger holes, and allow the new seals to
fit, then the new flanges can be used, and the trans will be converted to
100mm. You can also choose to do this and then use new style 90mm flanges,
to replace the old style 90mm flanges.

Some older trans will need grinding done on
the side of the case for the drivers flange to clear, RonP has some info
about the grinding, and also about converting the old trans to 100mm. Here
is a link to Ron's page which has info on converting an older trans to use
the new seals...
http://scirocco.dyn.dhs.org/cheapassron/020tranny/flanges.htm